Sidelink positioning in unlicensed band

The present invention a method of a first radio node for sidelink positioning using an unlicensed band, and an associated method of a second radio node, and associated devices, systems, computer program elements, and non-transitory computer readable media.

Connected mobility is the subject of a variety of communication standards such as IEEE 802.11p/bd and 3GPP LTE/NR V2X (shortened in this specification to “V2X”). Two scenarios are considered for V2X—that User Equipment (UE) can be within communication range of a base station (BS) such as an evolved-Node BS (eNB) or a 5G-NR-Node BS (gNB), or out of communication range. Another scenario is that a proportion of the UEs that are connected together may be connected to the network, and the remainder of the UEs that are connected together may be out of network coverage. This is referred to as partial out of coverage.

Typically, when a UE (for example, UE mounted in a vehicle) is in coverage, the UE can be configured to perform sidelink communication with other UEs in range. In this case, resource allocation, data control, and communication procedures are controlled by the UE. In the case that a UE is out of coverage of, for example, EUTRA or 5G-NR cells, the UE is pre-configured with mandatory configuration for autonomous communication using the sidelink. In example, a UE can be pre-configured with a number of out-of-coverage frequencies. As an example, the out-of-coverage frequencies may include the Intelligent Transport System (ITS) frequencies.

1 FIG. 1 FIG. 8 schematically illustrates an example of a radio network. In this example, the network comprises a “V2X” configured sidelink utilizing mode 1 and mode 2, although it will be appreciated that the scenario ofmay be extended to other radio standards using a sidelink between radio nodes that are out of coverage.

10 12 14 1 2 3 4 5 6 Regionis outside of network coverage provided by a BS. Regionis a region of partial coverage. Regionis in coverage. UEis a radio node that communicates with UEvia a sidelink channel in mode 2, for example. UEcommunicates from the region of partial coverage to an out-of-coverage UEvia the sidelink channel in Mode 2. UEcommunicates with UEvia a sidelink channel in mode 1, as configured by control information Uu from the BS.

Identifying the position of a radio node with respect to another radio node is of interest in many scenarios. Wireless standards such as 3GPP Release 16 enable the UE to be configured with a downlink Position Reference Signal (PRS) having a high resource element (RE) density that is suitable for positioning calculations. The patterns of the PRS are referred to as combs, and are typically defined by the distance between two PRS REs, and an offset over time. Positioning approaches in 3GPP mobility scenarios may, however, be further improved.

transmitting, from the first radio node, a sidelink position reference signal configuration defining at least one position reference signal to be transmitted from a first radio node to the second radio node; generating at least one position reference signal as defined by the SPRS configuration transmitted to the second radio node; performing channel contention for the purpose of position reference signal transmission in a bandwidth range at least partially comprised in an unlicensed radio band, wherein the contention is performed using a listen before talk mechanism; based on a positive result of the channel contention, accessing the channel for the duration of a channel on time; and transmitting the at least one position reference signal to the second radio node during the channel on time. According to a first aspect of the present invention, there is provided a method of a first radio node. According to an example embodiment of the present invention, the method includes:

An effect is that positioning may be performed over a side link by transmitting side link position reference signals in unlicensed carrier bands. This leads to an improved position resolution because a side link position reference signal comb can be detected and decoded with improved position resolution if it covers a wider bandwidth. The application of channel sensing enables the improved position resolution to be achieved without interference with higher priority users of the unlicensed bands. This enables the many regulatory requirements required to access the unlicensed spectrum to be preserved (such as a nominal bandwidth, and contiguous nominal carrier aggregation by the same device). The technique detailed herein is flexible, and can be applied to different nominal bandwidths and different nominal aggregate bands as specified between different regions. For example, the ETSI BRAN regulations mandate a nominal frequency of 20 MHz and 4, 8, 16 etc aggregated bands in the 5 GHZ and 6 GHz frequency bands, although the technique discussed herein may be generalised to other regions.

In other words, the first problem addressed is that cycling is limited to dedicated (ITS) and licensed bands. In this case, unlicensed bands can be used to complement the ITS/licensed bands.

The second problem is that it is difficult to guarantee wideband carriers for side link positioning simultaneously with communication carriers. In this case, unlicensed wideband operation can be used to increase the available bandwidth important for enhancing the positioning accuracy.

The third problem is that of initiating a channel on time (COT), and sharing a channel on time (COT). According to this specification, if a side link position reference signal (SPRS) is scheduled, a radio node shares its channel on time for sending the SPRS with other radio nodes, where the other radio nodes use the transmission opportunity with a short time gap so as not to lose the channel contention. If the channel contention by the first radio node fails, a second radio node will not detect the first radio node's SPRS.

transmitting, to a first radio node, a sidelink position reference signal configuration defining at least one position reference signal to be transmitted from the first radio node to the second radio node; and receiving at least one sidelink position reference signal transmitted by the first radio node in a bandwidth range at least partially comprised in an unlicensed radio band, wherein the at least one sidelink position reference signal is defined according to the sidelink position reference signal configuration. According to second aspect of the present invention, there is provided a method of a second radio node. According to an example embodiment of the present invention, the method comprises:

According to a third aspect of the present invention, there is provided a first radio node. According to an example embodiment of the present invention, the first radio node comprises a radio modem, non-transitory computer readable media comprising machine readable instructions, and a processor configured to load and to execute the machine readable instructions to cause the first radio device to execute the method according to the first aspect, or its embodiments, and thus to transmit a modified position reference signal to a second radio device via at least one side link channel.

According to a fourth aspect of the present invention, there is provided a second radio node. According to an example embodiment of the present invention, the method comprises a radio modem, non-transitory computer readable media comprising machine readable instructions, and a processor configured to load and to execute the machine readable instructions to cause the second radio device to execute the method according to the second aspect of the present invention, or its embodiments.

According to a fifth aspect of the present invention, there is provided a system for radio communication. According to an example embodiment of the present invention, the method comprising a first radio node as defined by the third aspect, and a second radio node as defined by the fourth aspect of the present invention.

According to a sixth aspect of the present invention, there is provided a computer program element. According to an example embodiment of the present invention, the method comprises machine readable instructions which, when loaded and executed by a processor, cause the processor to perform the method according to the first aspect according to the present invention.

According to a seventh aspect of the present invention, there is provided a computer program element. According to an example embodiment of the present invention, the computer program element comprises machine readable instructions which, when loaded and executed by a processor, cause the processor to perform the method according to the second aspect of the present invention.

According to an eighth aspect of the present invention, there is provided a non-transitory computer readable medium, According to an example embodiment of the present invention, the method comprises the machine readable instructions of the sixth or seventh aspects.

According to a ninth aspect, there is provided a vehicle, comprising a radio communications node according to one of the third or fourth aspects of the present invention.

The present specification therefore proposes two general techniques to access unlicensed frequency bands for side link positioning. The first technique uses licensed (ITS) or dedicated carrier assisted access, where a licensed or dedicated carrier is used on the side link to control the transmission of positioning signals on unlicensed spectrum. The dedicated carrier may also be used to send broadcast information. A further technique is discussed, in which control and positioning signals are both sent on unlicensed spectrum without requiring licensed (ITS) or dedicated carrier assisted access.

1 FIG. schematically illustrates an example of a “V2X” configured system comprising a sidelink that can be configured into mode 1 and mode 2.

1 2 The radio standard 5G New Radio (5GNR) provides for a network comprising a next generation node base station (gNB) and a set of User Equipment (UE, UE. . . ). The gNB is used for controlling of communicating data to some, or all of the UEs via the Uu interface. The Uu interface may be considered to be a communication link between a gNB and another network terminal UE. In examples, the UE terminal (also referred to herein as a radio node) may be an IoT device, a vehicular infrastructure element, an industrial automation component, or an industrial infrastructure element. Examples of vehicular infrastructure elements are traffic lights, and streetlights. Examples of an industrial infrastructure element are robots or industrial machines. The UE terminal may be a mobile telephone, laptop computer, tablet, smartwatch, or the like. The UE terminal may be embodied within a vehicle such as an automobile, heavy goods vehicle, bicycle, and the like.

1 2 2 2 2 1 2 1 The 3GPP standard provides for the transmission of signals between first and second radio nodes enabling the second radio node to determine its position relative to a first radio node, for example. The signals are typically referred to as “combs” owing to their structure in frequency and time. The first radio node UEmay be requested by the second radio node UEto transmit a position reference signal (PRS) having a comb structure known at the second radio node UE. When the second radio node UEreceives the requested PRS from the first radio node, a decoding technique such as downlink angle of departure (DL-AoD), uplink angle of arrival (UL-AoA), Round Trip Time (RTT), downlink Time of Arrival (DL-ToA) or uplink Time of Arrival (UL-ToA) may be applied by the second radio node UEto the PRS transmitted by the first radio node UE. This enables the second radio node UEto determine its position relative to the first radio node UE.

Current implementations of positioning using the PRS only support positioning for classical cellular scenarios, such as positioning between the gNB (base station, BS) and mobile radio nodes UE. Vehicular and industrial applications, when out of coverage (or in partial coverage) of a gNB (base station, BS) require inter-UE positioning without involving the gNB. The present specification details an approach for using the PC5 sidelink to support inter radio-node positioning.

2 FIG. schematically illustrates an example of time and frequency resource configuration of the sidelink in mode 2.

16 17 15 16 The sidelink resource allocationin mode 2 is divided into frequency resource blocks (ranges of subchannels) FRE and time slots TRE. In an example, a subsetof the sidelink resource allocation in mode 2 is configured by the gNB. Another subsetof the resource allocation is dedicated to autonomously used resources accessed by the radio nodes UE. In an example, one or more UEs may use semi periodic scheduling of the sidelink resource allocationto contend for sidelink resources. In mode 2, resources can be allocated as a one-shot transmission, where the UE transmits into the gNB controlled resource or the autonomously allocated resource as a MAC-PDU because available. In another example, configured sidelink resources may enable a UE to transmit multiple MAC-PDUs on multiple transmission opportunities.

5 5 3GPP, release 16, proposed Position Reference Signal configurations, for example, defining the structure of a PRS signal during the downlink and/or uplink between UE and a gNB (BS). The Position Reference Signal configuration also defines on which OFDM symbol and subcarriers the PRS may be found. A PRS positioning frequency layer is defined as a collection of PRS resource sets with each PRS resource set defining a collection of PRS resources. When applied to localisation between a radio node such as a gNB and a radio node such as item of user equipment UE, one or more downlink Position Reference Signals are used at UEtransmitted from the gNB (BS). The 3GPP release 16 PRS has a high resource element density having a diagonal or staggered PRS pattern and correlation properties that are better than existing reference signals.

1 2 1 2 1 2 The improved PRS signal of 3GPP release 16 cannot be mapped to the problem of position determination between first and second radio nodes UE, UEvia the sidelink in mode 2. In Base Station (gNB) coordinated positioning, the base stations can coordinate which comb patterns from the PRS set, with which offset, are used by the base station, and associated UEs. This prevents a given UE from experiencing a collision of two different PRS at the same time. However, to apply the PRS directly to position determination between first UEand second UEradio nodes using the sidelink resource pool is problematic because the sidelink resource pool resource selection is performed between at least two UEs autonomously, usually using a distributed contention protocol such as semi persistent scheduling. Therefore, at least two UEs can pick the same offset for transmitting the same PRS pattern, for example. This results in an allocation of overlapping PRS resources. Thus, the sidelink PRS cannot be resolved between UEand UE, degrading the positioning performance.

Furthermore, the PRS comb structure defines the spacing of the PRS for a distinct user. This defines how many users can share one PRS block. There is, therefore, a trade-off between the number of users engaging in positioning using a number of PRS patterns using the same sidelink resource pool, and the performance of the ranging itself.

3 FIG. schematically illustrates colliding resources of a sidelink position reference signal (SPRS) from an RX UE perspective.

3 FIG. 20 1 23 22 1 2 3 21 21 21 21 21 24 a b a b c In, regionis a time-frequency plot representing of a portion of the resource grid of a sidelink resource pool from the RX perspective of a first radio node UE. The subchannel index is illustrated along frequency axisand the time (slot) index indicated along time axis. An OFDM slot of multiplexed SPRS from three radio nodes UE, UE, and UEis illustrated. Regionsandof the sidelink resource pool are areas with data symbols (that are not used for position determination), a gap, or blank symbols. For example, regionsandare regions of licensed bandwidth, and regionrepresents a region of unlicensed bandwidth for the transmission of SPRS according to the techniques discussed subsequently. The hatched symbolsrepresent a colliding SPRS.

The technique of this specification is applicable to radio nodes defined according to 3GPP REL-16 NR for unlicensed access, as in RP-201834. In an embodiment, the first and second radio nodes comply with scenario A: carrier aggregation between licensed band NR (PCell) and NR-U (SCell). In an embodiment, the first and second radio nodes comply with scenario B (dual connectivity between licensed band (PCell) and NR-U (PSCell). In an embodiment, the first and second radio nodes comply with scenario C (stand-alone NR-U). In an embodiment, the first and second radio nodes comply with scenario D (a stand-alone NR cell in unlicensed band and UL in licensed band. In an embodiment, the first and second radio nodes comply with scenario E (dual connectivity between licensed band NR and NR-U).

In LTE, licensed assisted access for the downlink was initially introduced using “listen before talk” (LBT) to avoid collision with existing transmission in the unlicensed bands. Licensed assisted access enhancements (eLAA) introduced LBT on the uplink. 5G new radio introduces unlicensed operation for both uplink (UL) and downlink (DL) either in licensed coverage or unlicensed coverage. In this case, a radio node such as a UE or qNB starts an LBT channel sensing to discover nearby interference. After winning an LBT, either the gNB or the UE initiate a channel occupancy time (COT). A COT is dependent on many factors, such as the frequency of LBT-false, the number of HARQ NACKS, etc. during the COT, the UE or gNB transmit their UL or DL, simultaneously.

NR for unlicensed operation introduces two approaches for channel sharing based on supported traffic needs: a load-based event LBE or a frame-based event FBE COT. In LBE, either the UE or gNB access the channel after a successful LBT when there is data to be transmitted in the uplink or downlink. In this case, the radio node is only able to start an LBT directly before a pre-scheduled UL-grant to be able to occupy its scheduled time slot. In a not very different occupancy and granting procedure, FBE is performing an LBT in a time deterministic manner, however a COT is shared with the other devices to send feedback or return traffic.

The COT sharing between uplink and downlink has to guarantee a short time gap between the traffic direction switching between a first device (initiating the COT) and a second device (sharing the same COT) such as not more than 16 μs. After such a gap, the second device is supposed to share the COT and send the opposite traffic after a short sensing interval (LBT-CAT2) or no sensing (LBT-CAT4). However, if a short LBT is mandated, the second device refrains from transmission if the LBT result is negative.

4 FIG.A schematically illustrates a method of a first radio node according to the first aspect.

40 1 41 1 72 83 1 2 transmitting, from the first radio node UE, sidelink position reference signal configuration,,defining at least one position reference signal to be transmitted from a first radio node UEto the second radio node UE; 42 2 generatingat least one position reference signal as defined by the SPRS configuration transmitted to the second radio node UE; 43 2 performingchannel contention LBT for the purpose of position reference signal transmission in a bandwidth range at least partially comprised in an unlicensed radio band F, wherein the contention is performed using a listen before talk mechanism; 44 based on a positive result of the channel contention, accessingthe channel for the duration of a channel on time; and 45 2 transmittingthe at least one position reference signal to the second radio node UEduring the channel on time. According to a first aspect, there is provided a methodof a first radio node UE, comprising:

The technique of the first aspect covers two approaches for enabling access to unlicensed bands for SPRS purposes.

1 2 1 2 The first approach handles data transmission and reception in a licensed band F, and the transmission of a side link ranging pilot transmission SPRS in an unlicensed band F. In an embodiment, the first radio node performs channel contention on a licensed carrier Fusing the first channel contention technique. In an embodiment, the unlicensed carrier Fsupports channel contention using another channel access mechanism for example LBT, Clear Channel Assessment CCA, or monitoring of the channel occupancy time COT.

In an embodiment where the channel access mechanism concerned monitoring the COT, channel access may be arranged as a frame-based event or a load-based event.

1 1 2 72 83 2 1 2 1 According to the first approach, the licensed band Fcarries information and configuration commands for SPRS symbols intended to be transmitted, for example, from a first radio node UEto a second radio node UE(such as an interlace pattern, and slot or a transmission schedule of the SPRS). Accordingly, the first radio node may conduct an SPRS configuration transmission,following regulatory requirements (such as LBT, CCA, COT determination) before transmission of the SPRS itself in the unlicensed band F. In an embodiment, a receiving radio node can decode information received in the licensed carrier Frelating to the side link positioning configuration (interlace pattern, slot and/or transmission schedule of the SPRS) in the unlicensed band F. The second radio node obtains the information received in the licensed carrier Fto assist the second radio node to tune to the side link positioning transmission opportunity TO.

5 FIG. 1 1 1 1 2 In the first approach, an optional mode is fully arbitrary (the embodiment illustrated in). In this embodiment, a first radio node UEor group of radio nodes UE-Gmay signal an intention to schedule one SPRS pattern configuration (for example, one SPRS pattern out of a total of N possible patterns enabled by the relevant interlace) at a certain synchronised sidelink slot SL TX. In this embodiment, the first radio node UEor group of radio nodes UE-Gare configured to sense the unlicensed carrier Ffor free channel access using a channel contention mechanism and to send at least one SPRS without mandating for short-control or physical control information. The assumption is that all necessary control information has been conveyed via signalling in carrier one.

1 1 1 1 In a quasi-asynchronous variation of the foregoing example, there is a possibility to advance from synchronised and unicast or group cast of the sidelink communication on the licensed carrier F. In an embodiment, a first radio node UEmay select its SPRS position in time and frequency based on a pre-configuration or a dynamic network configuration. In an embodiment, the first radio node UEinitiates channel contention, such as LBT, to assess the availability of a free SPRS transmission opportunity. The first radio node UEsends an SPRS signal or pattern to cover a predetermined percentage of the nominal frequency. For a group of radio nodes UEs, each radio node may select a different SPRS format definition (interlace pattern) to use in the same percentage of the nominal frequency, so that the transmission by the SPRS group of UEs multiplex themselves on the same resources. In an embodiment, the interlace structure of the SPRS is chosen randomly by each radio node in the group of radio nodes to avoid collisions between SPRS patterns.

1 In an embodiment, a radio node, or group of radio nodes, are configured with a possible set of SPRS format definitions (set of interlace structures for the SPRS) and a reservation procedure for each SPRS format definition in the set of SPRS format definitions. A group of radio nodes is configured to select from the SPRS format definitions and reserve their respective selections in a reservation field. Then, each radio node transmits this reservation by signalling to other radio nodes via side link signalling. In an embodiment, one or more radio nodes in a group of radio nodes UE-G perform channel contention using, for example, LBT, to assess an availability of a free SPRS transmission opportunity (SPRS-T. . . ) schedule for this pattern. If free, the first radio node starts an SPS transmission to block the free SPRS transmission schedule.

1 In an embodiment, the SPS may be preceded optionally by a preamble or a short control information transmission. If other scheduled radio nodes are able to detect the initial transmission, and can decode the initial COT information signalled in the licensed band For optionally preceding the SPRS in a short control information, the next scheduled radio node UE or group of radio nodes UE-G can share the channel occupancy time as long as the channel occupancy time is not finished.

2 2 2 1 2 2 In the second approach, a self-organised channel access technique for side link positioning in the unlicensed band Fis considered. In this approach, the unlicensed carrier Fis used exclusively for side link positioning, or the unlicensed carrier Fis used for a combination of cycling positioning and data communication. According to the second technique, synchronisation via the communication exchanges on the licensed carrier Fis not required. In an embodiment, radio nodes may synchronise using the unlicensed carrier Fby sending broadcast and/or synchronisation information on the unlicensed carrier F.

2 1 2 In an embodiment, synchronisation on the unlicensed carrier Fcomprises 3GPP synchronisation techniques. For example, synch to synch master/GNSS, synch to gNB (broadcasting the synch signal in either of the licensed or unlicensed bands), synch to a synch source UE, and the like. The synchronisation signalling can be exchanged to the licensed carrier F. In an embodiment, if only unlicensed carrier Fis available and no other synchronisation sources are available, synchronisation between radio nodes can be conducted via configuring the resource pool in mode 2 (but in the unlicensed band) and exchanging a synchronisation sequence before engaging in positioning.

1 1 2 1 According to the second approach, the SPRS is transmitted asynchronously. The first radio node UEor group of radio nodes UE-G simultaneously perform a channel contention technique, for example LBT, and one or more of radio nodes UEdiscover the unlicensed band Fto be free. In this case, the first radio node UEwith a winning channel contention may allocate one out of N total SPRS format definitions (interlace patterns) in frequency. In an embodiment, the SPRS format definitions may be selected randomly. The selected pattern in time and frequency is, following a successful training contention, used to transmit the short control and SPRS structure. Other radio nodes can only receive short control and/or SPRS transmissions or try to capture the channel to send SPRS and/or short control.

1 1 9 FIG. In an embodiment, channel occupancy time-sharing of a radio node needing to send an FBE or LBE SPRS is performed. The first radio node UEor group of asynchronous radio nodes UE-G sense the channel using an initial channel contention process. Based on the success of the channel contention process, the first radio node or group of asynchronous radio nodes select 1 out of N SPRS format definitions (interlace patterns) and perform short-control transmission and SPRS. Any other station (or group of stations) which are sensing the network and are able to decode possible short information (with a COT duration) and SPRS may share the initial initiated COT by UEand send their SPRS following also an SPRS format definition. Other radio nodes or groups of radio nodes may share the initiated initial channel occupancy time COT as far as the COT is sufficient for more SPRS and/or short-control transmission. In case of an FBE, the initiated COT may send some information about the periodicity of the SPRS, i.e, wherein the initial procedure is repeated before each period, as illustrated inbelow.

1 1 2 2 According to an embodiment, the first radio node UEis configured to use a side link (such as a 5G NR sidelink) in the licensed band F(ITS or licensed carrier). According to an embodiment, the second radio node UEis configured to use a side link to perform side link positioning on the unlicensed carrier F.

Embodiments of the first radio node concerns a method in which the transmission opportunity of an SPRS is provided so that the transmission opportunity is concurrent with the transmission or reception in another carrier. Additionally, embodiments specify the behaviour of the first radio node for channel contention (such as listen before talk) in the case of a win or fail.

1 2 1 10 12 14 1 1 2 1 The following description discusses five options. Options one, two, and three concern embodiments in which the licensed band Fis dedicated to assisting positioning in the unlicensed band F. In such case, it is expected that the licensed or dedicated side link band Fis used to convey data and control signals to radio nodes in the immediate neighbourhood,,of the first radio node UE. It is also assumed that subsequent control signals on the licensed or dedicated band Fcarry configuration information in respect of the unlicensed side link band Fthat is dedicated for positioning. Options four and five concern unlicensed side link positioning embodiments that do not require communication in the licensed side link band F.

5 FIG. schematically illustrates a first example of establishing an SPRS exchange on an unlicensed carrier.

72 83 According to an embodiment, there comprises obtaining, from the SPRS configuration,, the synchronisation of the at least one position reference signal to at least one transmission opportunity of the side channel, and

2 transmitting the at least one position reference signal to the second radio node UEduring the channel on time. if the channel contention LBT for the purpose of position reference signal transmission is positive during the at least one transmission opportunity of the side channel:

1 2 According to an embodiment, at least the first UEand second UEradio nodes are members of a 5G NR radio network.

1 According to an embodiment, the licensed radio band Fcomprises a vehicle to everything V2X sub band of the 5G NR radio network.

2 According to an embodiment, the unlicensed radio band Fis comprised within at least one of the following ranges: 5150-5925 MHz; 5150-5350 MHZ (WAS/RLAN); 5470-5725 MHZ (WAS/RLAN); 5725-5855 MHZ (FWA); 5855-5875 MHz; 5875-5925 MHz (ITS), 5150-5250 (U-NII-1) 5250-5350 (U-NII-2A) 5350-5470 (U-NII-2B) 5470-5725 (U-NII-2C) 5725-5850 (U-NII-3) or 5850-5925 (U-NII-4).

1 2 According to an embodiment, the first UEand/or second radio UEnodes operate in either Frame Based Equipment mode or Load Based Equipment mode.

5 FIG. 1 2 1 70 70 2 2 1 2 2 1 61 2 71 2 1 2 is a time-frequency matrix that denotes channel events on licensed carrier Fand unlicensed carrier Fat the same time. According to a first technique, data transmission and reception and/or control transmission and reception is handled in the licensed carrier F. RegionsA,B define areas of the unlicensed band Fthat contained no transmission, or other technologies such as Wi-Fi(™) or other signals transmitted in the unlicensed band Fby other UE groups. SPRS-T, SPRS-Tcorrespond to potentially configurable SPRS transmission opportunities on the unlicensed band F. In the licensed band F, axisdefines SL slots to which the second radio node UEis synchronised in a SYNC operation. For the purposes of this example, it is assumed that only one UE group is present in the unlicensed band Fcomprising the first radio node UEand the second radio node UE.

1 2 1 2 1 For example, in the first option, data and/or control and limited configuration for the SPRS are communicated from the first radio node UEto the second radio node UEvia the licensed band F(SL RX, SL TX). The unlicensed band Fcarries the SPRS according to transmission opportunity TO that is relatively positioned to synchronisation control signals received in the licensed band F. According to the first option, channel occupancy time COT sharing is not performed, with the unlicensed band used for LBE. In this option, the first and/or second radio nodes communicate in load-based equipment mode LBE.

1 72 83 2 80 1 1 2 1 2 According to the embodiment of option 1, the licensed band carrying the side link Fcarries an SPRS configuration,for the SPRS (SLTX, SLRX) that will be transmitted in the unlicensed band F. For example, the licensed band carries a possible SPRS signal format defining an interlace pattern, the channel on time, and expected potential positioning opportunities. One or more of the signals may be referenced to the configured synchronisationof the carrier transmitted in the licensed band Fincluding, for example, the slot configuration). When the first radio node UEaccesses the unlicensed carrier UE, the channel contention operation performed by the first radio node UE(such as LBT) should be started early enough to enable synchronised transmission of an SPRS on the unlicensed carrier UEin the event that the LBT is successful.

2 1 1 70 2 1 1 2 1 1 2 1 2 2 If the channel contention in the unlicensed band F(LBT) is successful, the first radio node UEshall send the SPRS within the possible Tx opportunity (for example, SPRS-TinA). If the channel contention in the unlicensed band F(LBT) is not successful, the first radio node UEextends the channel contention window LBT-E (corresponding to the clear channel assessment CCA) until the first radio node UEsuccessful in the channel contention for the unlicensed carrier F. Then, the first radio node UEtransmits the SPRS without extending the possible SPRS window SPRS-T. If the channel contention for the unlicensed carrier Fis not won before the possible SPRS transmission opportunity is finished, the first radio node UEshall cancel the SPRS transmission and configure a new opportunity SPRS-T. In this case, the new opportunity is also an LBE-based transmission in the unlicensed band F.

5 FIG. 1 1 As shown in, a first group of radio nodes UE-Gis optionally provided. When a radio node UE is transmitting an SPRS in this group, it may apply a interlace pattern toe each SPRS that is orthogonal to the pattern of other radio nodes UEs within the same group UE-G. Therefore, if two radio nodes select the same pattern, it is optionally possible that the collision is resolved using a different orthogonal code for each radio node.

6 FIG. schematically illustrates a signalling protocol establishing an SPRS exchange on an unlicensed carrier utilizing control signals sent on the licensed carrier.

6 FIG. 1 2 1 2 1 71 1 2 1 72 2 1 73 74 2 1 75 2 71 75 2 1 2 For example,illustrates the process of transferring signals between a first radio node UE, a second radio node UE, related to licensed band Fand an unlicensed band F. Initially, the first radio node UEtransmits time synchronisationSYNC on the licensed band Fto the second radio node UE. The first radio node UEtransmits an SPRS configurationcomprising control data and/or a first SPRS configuration message to the second radio node UE. The first radio node UEperforms channel contention,on the unlicensed band Fand if the channel contention is successful, the first radio node UEtransmits an SPRSto the second radio node UEwithin the SPRS-TO defined by the synchronisation. The SPRStransmitted corresponds to the definition of the previously signalled SPRS configuration. For example, the SPRS configuration may comprise a description of the SPRS comb to be transmitted in terms of occupied bandwidth, occupied slots, interlace definition, and the like. The SPRS is received by the second radio node UEmay be used to compute the relative position of the first radio node UErelative to the second radio node UE.

74 1 2 77 2 76 1 76 1 2 2 1 1 2 If the channel contentionis not successful, the first radio node UEattempts a discrete number of further channel contention operations in the unlicensed band F. In an embodiment, following a permitted time gaprelative to the channel on time COT initiated relative to the transmission of the first SPRS, the second radio node UEtransmitsa further SPRS to the first radio node UE. In an example, the SPRScorresponds to the definition of the previously signalled SPRS configuration. In another example (not shown), either the first radio node UEor the second radio node UEmay engage in signalling to negotiate a different SPRS configuration for the SPRS transmitted from UEto UE. The response can be used by the first radio node UEto compute its position relative to the second radio node UEaccording to conventional techniques such as RTT.

72 83 2 1 According to an embodiment, the SPRS configuration,is transmitted to the second radio node UEvia a sidelink channel in a licensed radio band Fof a radio access network.

72 83 1 According to an embodiment, the SPRS configuration,is transmitted by the first radio node UEvia at least one of Physical Sidelink Shared Channel PSSCH, a Physical Sidelink Control Channel PSCCH, a Physical Downlink Shared Channel PDSCH, a Physical Downlink Control Channel PDCCH of the radio access network, or a Physical Sidelink Broadcast Channel PSBCH.

1 2 2 1 A variant of option one is now discussed as option two. According to the second option, in which the SPRS transmission is quasi asynchronous, the licensed band Fcarries data, control, and configuration of the SPRS when transmitted on the unlicensed band F. The unlicensed band Fcarries SPRS having a scheduled relative to a transmission opportunity defined in the synchronisation of the licensed band F. This may be applied to FBE or LBE-type COT sharing.

7 FIG. schematically illustrates a second example of establishing an SPRS exchange on an unlicensed carrier according to a second option.

2 80 76 87 1 1 transmitting, to the second radio node UE, a periodicity specifierdefining a plurality of further position reference signal,transmission opportunities of the first radio node UE, and/or a plurality of further radio nodes relative to an initial position reference signal transmission opportunity SPRS-T; 1 performing, at the first radio node UE, a plurality of further channel contention LBT operations corresponding to each of the plurality of position reference signal transmission opportunities; based on a positive result of at least one of the further channel contention operations, accessing the channel for the duration of the channel on time; and 76 87 2 80 transmitting at least one further position reference signal,to the second radio node UEduring the channel on time as defined by the periodicity specifier. According to an embodiment, the method comprises:

62 1 2 2 1 1 1 1 According to the second option, the first radio node UEconfigures a periodicity of its SPRS transmissions in the unlicensed band F. This corresponds to a frame-based equipment FBE mode on the unlicensed band F. Accordingly, a further radio node may schedule transmission of its further SPRS by utilising the channel on time COT signalled by the first radio node UE. This can be referred to as COT sharing. In this case, radio nodes in the group UE-Gdo not need to maintain a gap between their SPRS transmissions suitable for COT sharing. If the first radio node does not share its channel on time COT in the licensed band F, other radio nodes in UE-Gwill not be able to share the channel on time and may need to perform channel contention (LBT) for each transmission.

7 FIG. 1 1 1 2 1 2 1 1 2 2 2 1 2 1 1 As shown in, the first radio node UEpre-configures, or signals in a licensed band Fan SPRS for multiple user groups UE-G, UE-G, UE-GK. In an example, an initial transmission in respect of an SPRS in a first user group UE-Gscheduled in the unlicensed band Fusing LBT CAT-4 type channel contention for the initial transmission, and LBT-CAT-2 or CAT-1/0 for other SPRS group transmissions sharing the COT of the initial transmission. In general, an embodiment at least one radio node UEcomprised in a first group UE-Gof radio nodes performs an initial SPRS transmission in the unlicensed band Fusing a first type of channel contention, and a second group UE-Gof radio nodes performs a subsequent SPRS transmission in the unlicensed band Fusing a second type of channel contention. In an embodiment, at least the first group of radio nodes UE-Gand the second group of radio nodes UE-Gshare the channel on time initiated by a radio node UEin the first group of radio nodes UE-G.

2 76 87 1 transmitting, to the second radio node UE, a schedule of further position reference signal,transmission opportunities of the first radio node UE, and/or a plurality of further radio nodes; 1 performing, at the first radio node UE, a plurality of further channel contention LBT operations corresponding to each of the plurality of position reference signal transmission opportunities; based on a positive result of at least one of the further channel contention operations LBT, accessing the channel for the duration of the channel on time; and 76 87 2 transmitting at least one further position reference signal,to the second radio node UEduring the channel on time as defined in the schedule of further position reference signal transmission opportunities. According to an embodiment, the method comprises:

7 FIG. 1 2 1 2 1 2 1 2 2 A variant of the second option, as now discussed as the third option, also illustrated by. In this embodiment, the first radio node UE(or in other words, the radio node that performs channel contention first in the unlicensed band F) is configured to share its channel on time COT within the time period designated SPRS-T, SPRS-T, and to configure a periodically active transmission instance for a plurality of radio nodes UEs in one or more user groups UE-G, UE-G. Every other radio node UE may share the channel on time provided the channel on time has not expired, and no longer than the allowed gap is left between one UE and the next UE. If, unintentionally, a gap is left between one radio node UE sharing a previously organised on time, channel contention is mandated. Therefore, option three may be considered to be a synchronous S mode in which the licensed band Fcarries data, control and expected configuration of the SPRS on the unlicensed band F, and the unlicensed band Fcarries SPRS that are strictly scheduled to transmission opportunities, as may be useful with an FBE mode.

1 According to an embodiment, the channel contention LBT performed by the first radio node UEfor the purpose of position reference signal transmission is a category 4 listen before talk operation.

1 76 87 According to an embodiment, the channel contention LBT performed by the first radio node UEfor the purpose of further position reference signal,transmission opportunities is a category 2 listen before talk operation.

Options concerning the second approach in which channel access for SPRS is negotiated without use of the licensed band are now discussed.

72 83 1 2 According to an embodiment, the SPRS configuration,transmitted by the first radio node UEis received in the bandwidth range of the unlicensed radio band F, during the channel on time associated with channel contention LBT for control signalling.

8 FIG. 1 schematically illustrates a fourth option of establishing an SPRS exchange on an unlicensed carrier. This does not require additional use of the licensed band F.

2 According to the fourth option, data transmission and SPRS transmission occurs on the unlicensed band F. Channel contention is performed every time a radio node sends control and data, or control data and SPRS, or only short control information followed by SPRS. Each time there is a normal control or short control, the first radio node signals the configuration of the SPRS (such as duration, pattern and the like, and COT duration).

8 FIG. 1 2 2 1 1 1 2 In, slots SL, SLin the unlicensed band Fdenote short control channels used to communicate the transmission of an SPRS from a first radio node UE. Following transmission of the short control channels SL, corresponding SPRS are transmitted, where the transmission of SPRS of a certain radio node is not coordinated with other radio nodes. The short control SL, SLand SPRS are only sent after channel contention (LBT). UE-A, UE-B denote individual radio nodes.

63 1 2 2 1 1 1 2 According to the third option, the first radio node UEshares its channel on time in the unlicensed band Fwith other radio nodes, and may configure SPRS periodically using control signals transmitted in the unlicensed band F. In this embodiment, there are no dedicated transmission opportunities, and the channel on time between radio nodes is shared. At least one other radio node UE may share the channel on time COT of the first radio node UEprovided the channel on time COT of the first radio node UEis not expired, and no longer than and allowed gap is left between transmission of the first radio node and the subsequent radio node. If, unintentionally, a gap is left between radio node UEsharing the unlicensed band Fand a following radio node, channel contention is performed.

9 FIG. 2 schematically illustrates a fifth option of establishing an SPRS exchange on an unlicensed carrier. According to the fifth option, both control and position signalling occur exclusively on the unlicensed band F. The initial SPRS with channel contention (LBT) is performed, in other words, once an initial transmission opportunity of an SPRS is detected by a radio node, the initial dedicated COT.

1 2 2 1 2 1 2 2 1 1 2 1 1 1 2 1 2 1 For example, a plurality of radio node groups UE-G, UE-G, to UE-GK perform group-cast communication and coordinated side link communication in the unlicensed band F. In this case, the SPRS is signalled, for example, in the short control channel SL, SLand the SPRS reference is sent following the control channel. The transmission of other SPRS radio node groups may share the channel on time COT of an initial SPRS transmission. The initial SPRS transmission may only be performed after channel contention. Therefore, in general, the fifth option provides a plurality of groups of radio nodes UE-G, UE-G, to UE-GK performing positioning on the unlicensed band Fa first radio node UEin a first group of radio nodes UE-Gforms channel contention LBT-E to initially access the unlicensed channel F, thus initiating a channel on time during SPRS-T, and in this time a first SPRS and control information SLis sent from the first radio node UE. Other radio nodes in other groups of radio nodes UE-G, UE-GK may then share the channel on time within SPRS-Tto transmit subsequent positioning signals. The initial access of the unlicensed channel Fis optionally performed using CAT-4 LBT. The subsequent access to the unlicensed channel within the channel on time within SPRS-Tis performed using LBT-short (CAT-2) signalling.

10 FIG. schematically illustrates another example of a signalling protocol for establishing an SPRS exchange on an unlicensed carrier, using control signals sent on an unlicensed carrier.

10 FIG. 1 2 3 2 80 1 81 82 83 2 3 3 2 2 84 88 1 3 2 89 88 3 3 2 In the example of, a first radio node UE, the second radio node UE, and a third radio node UEcommunicate via an unlicensed band F. Initially, a resource pool in the unlicensed band is configuredeither via a pre-configuration received from a UE or a gNB, or previously stored configuration. A first radio node UEforms channel contention (LBT)and, if successful, transmits a short control to configure subsequent signalling, and a first SPRS configurationto at least the second radio node UEand optionally the third radio node UE(the third radio node UEmay passively receive all SPRS transmitted by the first radio node UEand using for positioning). The second radio node UEtransmitsits SPRS within the allowed gapinitiated by the transmission of the short control and first SPRS. The first radio node UEand optionally the third radio node UEreceive the SPRS transmitted by the second radio node UE. If an amount of timegreater than the allowed gapelapses, then a third radio node UEmust perform a new channel contention operation UEin order to access the unlicensed band upon completion of the channel contention, the third radio node transmits a renewed short control S-CTRL and its SPRS on the unlicensed band F.

11 FIG. 100 schematically illustrates an example of an SPRS format definition.

11 FIG. 1 14 101 102 In, the position of resource elements comprised in an SPRS interlace pattern is defined according to time slots S-frequency subcarrier offsets K. The intervalis the number of OFDM symbols used to transmit the sidelink position reference signal (SPRS). The resource elementis a comb element forming part of a position reference signal.

The initial position reference signal may, for example, be an SPRS comb as defined according to 3GPP Release 16, as in TS 138.211, section 7.4.1.7, which is hereby incorporated by reference, although this is not essential.

The offsetting of subcarriers within the SPRS comb defined by A, B, C, D, E.

2 2 1 2 2 1 1 2 2 According to an embodiment, the SPRS used in all options above has an interlaced structure. The interlaced structure covers a predetermined percentage of the unlicensed band F. In an example, the SPRS may occupy 50%, 60%, 70%, 80%, 90%, 95% or 100% of the unlicensed band F. In an embodiment, each radio node group UE-G, UE-G, UE-GK discussed above comprises a set of radio nodes multiplexing their SPRS over the predetermined occupied percentage of the unlicensed band Fof nominal frequency (for example, 20 MHz). In an example, if all radio nodes in a radio node group UE-Gare transmitting their SPRS, the whole band is interleaved with SPRS resource elements. Otherwise, only radio nodes UEs within the radio node group UE-Gwhich succeed in the channel contention (LBT) for the unlicensed band Fcan share the SPRS portion of the unlicensed band Fusing an interlaced structure.

72 83 2 2 based on a positive result of the channel contention LBT for control signalling, accessing the channel for the duration of a channel on time associated with the channel contention; and 72 83 2 72 83 2 wherein transmitting the SPRS configuration,to the second radio node UEcomprises transmitting the SPRS configuration,in the bandwidth range of the unlicensed radio band (F), during the channel on time associated with the channel contention for control signalling. According to an embodiment of the first aspect, prior to transmitting the SPRS configuration,to the second radio node UE, performing channel contention LBT for control signalling in a bandwidth range at least partially comprised in an unlicensed radio band Fusing a listen before talk mechanism;

72 83 100 2 1 1 2 2 According to an embodiment, the SPRS configuration,comprises an SPRS format definitiondefining a proportion of resource elements of the unlicensed radio band Fto be occupied by the at least one position reference signal transmitted by the first radio node UE. The first radio node UEis configured to transmit, to the second radio node UE, at least one position reference signal defined by the SPRS format definition via a plurality of subcarriers in a bandwidth range at least partially comprised in the unlicensed radio band F.

100 2 According to an embodiment the SPRS format definitionhas a plurality of subsets each corresponding to a plurality of further radio nodes, wherein the SPRS format definition is designed to fully occupy the unlicensed radio band F, when all of the radio nodes in the plurality of further radio nodes obtain a positive result in a channel contention LBT operation.

100 1 1 2 1 According to an embodiment, the SPRS format definitiondefines a plurality of subsets of SPRS patterns. Each SPRS pattern corresponds to a further radio node in the plurality of radio nodes UE-G. The SPRS format definition by the first radio node UEdefines an SPRS that is distributed across a predetermined proportion of the unlicensed radio band F. A plurality of further radio nodes UE-Gare configured to interleave their respective SPRS transmissions according to the SPRS format definition to obtain a positive result in a channel contention (LBT) operation.

46 2 47 1 1 2 transmitting, to a first radio node UE, a sidelink position reference signal configuration defining at least one position reference signal to be transmitted from the first radio node UEto the second radio node UE; and 48 1 2 receivingat least one sidelink position reference signal transmitted by the first radio node UEin a bandwidth range at least partially comprised in an unlicensed radio band F, wherein the at least one sidelink position reference signal is defined according to the sidelink position reference signal configuration. According to a second aspect, there is provided a methodof a second radio node UE, comprising:

4 FIG.B schematically illustrates a method of a second radio node according to the second aspect.

72 83 1 1 According to an embodiment of the second aspect, the SPRS configuration,is transmitted to the first radio node UEvia a sidelink in a licensed radio band Fof a radio access network.

72 83 According to an embodiment of the second aspect, the SPRS configuration,is transmitted via at least one of a Physical Sidelink Shared Channel PSSCH, a Physical Sidelink Control Channel PSCCH, a Physical Downlink Shared Channel PDSCH, a Physical Downlink Control Channel PDCCH of the radio access network, or a Physical Sidelink Broadcast Channel PSBCH.

72 83 1 2 72 83 wherein the first radio node UEis configured to receive at least one position reference signal transmitted by the second radio node UEsynchronised to the at least one transmission opportunity of the side channel as defined in the SPRS configuration,. According to an embodiment of the second aspect, the SPRS configuration,defines the synchronisation of the at least one position reference signal to at least one transmission opportunity of the side channel, and

2 1 According to the above embodiment, a method of the second radio node UEis provided corresponding to the first option in which the data and/or control for arranging the SPRS are transmitted on a side link on the licensed band F.

72 83 80 2 76 87 2 receiving a plurality of further position reference signals,transmitted by a corresponding plurality of further radio nodes, wherein the plurality of further position reference signals occupy a plurality of subcarriers in a bandwidth range at least partially comprised in the unlicensed radio band F. According to an embodiment of the second aspect, the SPRS configuration,comprises a periodicity specifierdefining a plurality of further position reference signal transmission opportunities of the second radio node UE, and/or a plurality of further radio nodes relative to an initial position reference signal transmission opportunity; and

According to an embodiment of the second aspect, the SPRS configuration.

72 83 76 87 2 ,comprises a schedule of further position reference signal,transmission opportunities of the second radio node UE, and/or a plurality of further radio nodes.

2 1 According to an embodiment of the second aspect, the method further comprises calculating the position of at least the second radio node UErelative to the first radio node UEusing the at least one position reference signal transmitted by the first radio node.

2 1 According to an embodiment of the second aspect, the position of at least the second radio node UErelative to the first radio node UEis calculated using the angle of departure or round-trip time.

72 83 100 2 2 According to an embodiment of the second aspect, the SPRS configuration,defines an SPRS format definitiondefining a proportion of resource elements of the unlicensed radio band Fto be occupied by the at least one position reference signal transmitted by the second radio node UE.

100 1 1 2 1 According to an embodiment of the second aspect, the SPRS format definitiondefines a plurality of subsets of SPRS patterns. Each SPRS pattern corresponds to a further radio node in the plurality of radio nodes UE-G. The SPRS format definition by the first radio node UEdefines an SPRS that is distributed across a predetermined proportion of the unlicensed radio band F. A plurality of further radio nodes UE-Gare configured to interleave their respective SPRS transmissions according to the SPRS format definition to obtain a positive result in a channel contention (LBT) operation.

1 2 According to an embodiment of the second aspect, at least the first UEand second UEradio nodes are members of a 5G NR radio network.

2 According to an embodiment of the second aspect, the channel contention LBT returns a negative result in response to detecting the presence of a Wi-Fi, or Bluetooth transmission in the unlicensed radio band F, or other interfering signals.

1 According to an embodiment of the second aspect, the licensed radio band Fcomprises a vehicle to everything (V2X) sub band of the 5G NR radio network.

12 FIG. schematically illustrates an example of a first or a second radio node radio node according to the third and/or fourth aspects.

90 92 94 95 1 According to a third aspect, there is provided a first radio node, comprising a radio modem, non-transitory computer readable mediacomprising machine readable instructions, and a processorconfigured to load and to execute the machine readable instructions to cause the first radio device to execute the method according to the first aspect or its embodiments, and thus to transmit a modified position reference signal to a second radio device via at least one side link channel. The first radio node UEis, in an example, configured to communicate using at least a vehicle to everything (V2X) sub band of the 5G NR radio network, and to transmit sidelink position reference signals on a portion of unlicensed band.

1 According to a fourth aspect, there is provided a second radio node, comprising a radio modem, non-transitory computer readable media comprising machine readable instructions, and a processor configured to load and to execute the machine readable instructions to cause the second radio device to execute the method according the second aspect or its embodiments. The second radio node UEis, in an example, configured to communicate using at least a vehicle to everything (V2X) sub band of the 5G NR radio network, and to transmit sidelink position reference signals on a portion of unlicensed band.

90 93 91 90 97 92 90 The first and/or second radio communication devicemay comprise an input interfaceconfigured to obtain input data, for example commands from a higher layer to perform positioning. The radio communication devicemay comprise a power supply. The radio communication device may comprise an antennacoupled to the radio modem. The first radio device may support device to device, internet of things, and V2X communications.

8 1 2 8 According to a fifth aspect, there is provided a systemcomprising at least a first radio node UEaccording to the third aspect, and a second radio node UEaccording to the fourth aspect. The systemis, for example, configured to communicate using at least a vehicle to everything (V2X) sub band of the 5G NR radio network, and to transmit sidelink position reference signals on a portion of unlicensed band.

According to a sixth aspect, there is provided a computer program element comprising machine readable instructions which, when loaded and executed by a processor, cause the processor to perform the method according to the first aspect.

According to a seventh aspect there is provided a computer program element comprising machine readable instructions which, when loaded and executed by a processor, cause the processor to perform the method according to the second aspect.

According to an eighth aspect, there is provided a non-transitory computer readable medium comprising the machine readable instructions of the sixth or seventh aspects.

According to a ninth aspect, there is provided a vehicle, comprising a radio communications node according to one of the third or fourth aspects.

The examples provided in the drawings and described in the foregoing written description are intended for providing an understanding of the principles of this specification. No limitation to the scope of the present invention is intended thereby. The present specification describes alterations and modifications to the illustrated examples. Only the preferred examples have been presented, and all changes, modifications and further applications to these within the scope of the specification are desired to be protected.